Method and apparatus for bone fixation with secondary compression

ABSTRACT

Disclosed is a fracture fixation device, for reducing and compressing fractures in a bone. The fixation device includes an elongate body comprising a first portion and a second portion that are detachably coupled to each other. The first portion defines a helical cancellous bone anchor and the second portion defines a distal end. An axially moveable proximal anchor is carried by the proximal end of the fixation device and is rotationally locked to the first portion. The device is rotated into position across the femoral neck and into the femoral head, and the proximal anchor is distally advanced to lock the device into place. The second portion is then detached from the first portion.

PRIORITY INFORMATION

[0001] This invention is a continuation-in-part of U.S. patentapplication Ser. No. 09/822,803, filed Mar. 30, 2001, the entirecontents of which are hereby expressly incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to internal bone fracture fixationdevices. In one application, the present invention relates to bonefracture fixation devices and methods adapted for fixation, among otherfractures, of femoral neck and other proximal femoral fractures.

[0004] 2. Description of the Related Art

[0005] The femur, otherwise known as the thigh bone, generally comprisesan elongate shaft extending from the hip to the knee. The proximal endof the shaft includes a head, a neck, a greater trochanter and a lessertrochanter. The head of the femur fits into the acetabular cup of thehip bone to form a ball and socket joint at the hip. The distal end ofthe femur includes a medial condyle and a lateral condyle. The condylesengage an upper end of the tibia to form the knee joint. Overall, thefemur is the longest and strongest bone in the skeleton. However,portions of the femur are extremely susceptible to fracturing.

[0006] Pertrochanteric fractures among geriatric patients are the mostfrequent in connection with those of the region of the neck of the bone.The advanced age and the pathologies which are encountered in thesepatients make a timely stabilization of skeletal injuries necessary inorder to reduce to a minimum the bed confinement and the rehabilitationtimes. Preferably, devices and procedures are utilized which minimizecomplications brought about by the so-called immobilization syndrome,which may be lethal for patients in delicate metabolical circumstances.It is also preferable to reduce to a minimum blood losses related tosurgical intervention. At the same time, the syntheses means utilizedmust be stable in order to allow the patient to very timely assume aseated position and, two or three days following the intervention, toreassume an erect posture with progressive bearing of weight.

[0007] Internal fixation of femoral fractures in general is one of themost common orthopedic surgical procedures. Fractures of the femur occurin both the proximal portion of the femur and the distal portion of thefemur. Fractures of the proximal portion of the femur (hip fractures)are generally classified as femoral neck fractures, intertrochantericfractures and subtrochanteric fractures. Fractures of the distal portionof the femur (knee fractures) are referred to as supracondylarfractures. Supracondylar fractures generally extend vertically betweenthe condyles at the lower end of the femur to separate the distalportion of the femur into two main bone fragments. A fracture line maybe further comminuted to create a plurality of smaller bone fragments.Fractures of the femur which extend into the neck of the bone aregenerally more difficult to treat than fractures restricted to the shaftof the femur.

[0008] Operative treatment of the fractures requires that the fracturesbe internally fixed and possibly compressed. Fractures of the neck, heador trochanters of the femur have been treated with a variety ofcompression screw assemblies which include generally a compression platehaving a barrel member, a lag screw and a compressing screw. Thecompression plate is secured to the exterior of the femur and the barrelmember is inserted into a predrilled hole in the direction of thefemoral head. The lag screw which has a threaded end and a smoothportion is inserted through the barrel member so that it extends acrossthe break and into the femoral head. The threaded portion engages thefemoral head. The compressing screw connects the lag screw to the plate.By adjusting the tension of the compressing screw the compression(reduction) of the fracture can be adjusted.

[0009] A variety of elongated implants (nail, screw, pin, etc.) havebeen developed, which are adapted to be positioned along thelongitudinal axis of the femoral neck with a leading (distal) endportion in the femoral head so as to stabilize a fracture of the femoralneck. The elongated implant may be implanted by itself or connected toanother implant such as a side plate or intramedullary rod. The leadingend portion of the implant typically includes means to positively gripthe femoral head bone (external threads, expanding arms, etc.), but theinclusion of such gripping means can introduce several significantproblems. First, implants with sharp edges on the leading end portion,such as the externally threaded implants, exhibit a tendency to migrateproximally towards the hip joint weight bearing surface afterimplantation. This can occur when the proximal cortical bone hasinsufficient integrity to resist distal movement of the screw head. Suchproximal migration under physiological loading, which is also referredto as femoral head cut-out, can lead to significant damage to theadjacent hip joint. Also, the externally threaded implants can generatelarge stress concentrations in the bone during implantation which canlead to stripping of the threads formed in the bone and thus a weakenedgrip. The movable arms of known expanding arm devices are usually freeat one end and attached at the other end to the main body of the leadingend portion of the implant. As a result, all fatigue loading isconcentrated at the attached ends of the arms and undesirably largebending moments are realized at the points of attachment. In addition,conventional threaded implants generally exhibit insufficient holdingpower under tension, such that the threads can be stripped out of thefemoral head either by overtightening during the implantation procedureor during post operative loading by the patient's weight.

[0010] Thus, notwithstanding the variety of efforts in the prior art,there remains a need for an orthopedic fixation device with improvedlocking force such as within the femoral head in a femoral neckapplication, which resists migration and rotation, and which can beeasily and rapidly deployed within the bone.

SUMMARY OF THE INVENTION

[0011] There is provided in accordance with one aspect of the presentinvention, a method of securing a first bone fragment to a second bonefragment. The method comprises the steps of drilling a bore through thefirst bone fragment in the direction of the second bone fragment, andadvancing through the bore a fixation device comprising a first portionand a second portion that are coupled to each other. A distal anchor ofthe fixation device is rotated to secure the fixation device to thesecond fragment, and the proximal anchor is axially advanced to engagethe first fragment.

[0012] In one application of the method, the second bone fragmentcomprises the head of a femur. Alternatively, the second bone fragmentcomprises a tibia, a fibula, a femur, a humurus, a radius, or an ulna.The first bone fragment may comprise a condyle.

[0013] The method may additionally comprise the step of uncoupling thefirst portion from the second portion.

[0014] In accordance with another aspect of the present invention, thereis provided a femoral neck fracture fixation device. The devicecomprises an elongated body, having a proximal end and a distal end andcomprising a first portion and a second portion detachably coupled toeach other at a junction. The first portion includes an anti-rotationalstructure. A helical distal anchor is provided on the distal end. Afirst retention structure is provided on the body, proximal to thedistal anchor, and a proximal anchor surface is moveably carried by thebody. The proximal anchor includes a tubular sleeve that in a firstposition extends distally past the junction between the first portionand the second portion. The proximal anchor surface is moveable in thedistal direction with respect to the body. The retention structureresists proximal movement of the proximal anchor surface with respect tothe body, and the anti-rotational structure prevents rotational movementof the first portion with respect to the proximal anchor.

[0015] In one embodiment, the first retention structure comprises aseries of ridges or grooves. A second retention structure is preferablyprovided on the interior of the tubular sleeve for cooperating with thefirst retention structure on the body.

[0016] In accordance with a further aspect of the present invention,there is provided a bone fracture fixation device. The fixation devicecomprises an elongate body having a proximal end and a distal end andcomprising a first portion and a second portion that are detachablycoupled to each other at a junction. A cancellous bone anchor and/or acortical bone anchor is carried by the distal end. A proximal anchor isaxially moveably carried on the body and includes a tubular portion thatextends distally past the junction. Complementary surface structures areprovided in between the first portion of the body and the proximalanchor to permit advancing the proximal anchor in the distal directionto tighten the fixation device but resist axial proximal movement of theproximal anchor and to prevent rotational movement between the firstportion and the proximal anchor.

[0017] In accordance with another aspect of the present invention, thereis provided a method of treating a femoral fracture. The methodcomprises the steps of drilling at least one and preferably two or threebores distally into the femur in the direction of a fracture, andadvancing into each bore a fixation device that comprises a body havinga first portion that forms a distal bone anchor and a second portionthat forms a proximal end. A proximal component is rotated to engage thedistal anchor with the bone distal to the fracture, and a proximalanchor is advanced distally along the fixation device to compress thefracture.

[0018] Preferably, the drilling step comprises drilling the bore alongan axis which extends through the femoral neck and in the direction ofthe head of the femur. In one embodiment, the advancing a proximalanchor step comprises axially advancing the proximal anchor withoutrotating the proximal anchor with respect to the fixation device. Thefemoral fracture may be a femoral neck fracture (e.g., capital orsubcapital), an intertrochanteric fracture or a subtrochantericfracture.

[0019] Further features and advantages of the present invention willbecome apparent to those of skill in the art in view of the detaileddescription of preferred embodiments which follows, when consideredtogether with the attached drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 is a posterior elevational posterior cross section throughthe proximal portion of the femur, illustrating two femoral neckfracture fixation devices positioned therein.

[0021]FIG. 2 is a side perspective view of a fixation device similar tothat of FIG. 1.

[0022]FIG. 3 is a side elevational view of the fixation device of FIG.2.

[0023]FIG. 4 is a cross-sectional view taken through line 4-4 of FIG. 3.

[0024]FIG. 4A is an enlarged view of portion 4A of FIG. 4.

[0025]FIG. 4B is an enlarged view of portion 4B of FIG. 4 with thefixation device in a first position.

[0026]FIG. 4C is an enlarged view of portion 4C of FIG. 4 with thefixation device in a second position.

[0027]FIG. 5 is a cross-sectional view taken through line 5-5 of FIG. 3.

[0028] FIGS. 6A-C illustrate a procedure for using of the fixationdevice of FIG. 1 to secure a femoral neck fracture.

[0029]FIG. 7 is an anterior view of the distal tibia and fibula, withfixation devices similar to that of FIG. 1 arranged across lateral andmedial malleolar fractures.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0030] Although the fixation devices of the present invention will bedisclosed primarily in the context of fractures of the proximal femur,the methods and structures disclosed herein are intended for applicationin any of a wide variety of bones and fractures, as will be apparent tothose of skill in the art in view of the disclosure herein. For example,the bone fixation device of the present invention is applicable in awide variety of fractures and osteotomies in the hand, such asinterphalangeal and metacarpophalangeal arthrodesis, transversephalangeal and metacarpal fracture fixation, spiral phalangeal andmetacarpal fracture fixation, oblique phalangeal and metacarpal fracturefixation, intercondylar phalangeal and metacarpal fracture fixation,phalangeal and metacarpal osteotomy fixation as well as others known inthe art. A wide variety of phalangeal and metatarsal osteotomies andfractures of the foot may also be stabilized using the bone fixationdevice of the present invention. These include, among others, distalmetaphyseal osteotomies such as those described by Austin andReverdin-Laird, base wedge osteotomies, oblique diaphyseal, digitalarthrodesis as well as a wide variety of others that will be known tothose of skill in the art. The bone fixation device may be used with orwithout plate(s) or washer(s), all of which can be either permanent,absorbable, or combinations.

[0031] Fractures of the fibular and tibial malleoli, pilon fractures andother fractures of the bones of the leg may be fixated and stabilizedwith the present invention with or without the use of plates, bothabsorbable or non-absorbing types, and with alternate embodiments of thecurrent invention. Fractures and osteotomies of the mid and hind foot,tarsal arthrodesis and osteotomy, or others as are known to those withskill in the art. One example is the fixation of the medial malleolaravulsion fragment.

[0032] The fixation device of the present invention may also be used toattach tissue or structure to the bone, such as in ligament reattachmentand other soft tissue attachment procedures. Plates and washers, with orwithout tissue spikes for soft tissue attachment, and other implants mayalso be attached to bone, using either resorbable or nonresorbablefixation devices depending upon the implant and procedure. The fixationdevice may also be used to attach sutures to the bone, such as in any ofa variety of tissue suspension procedures.

[0033] For example, peripheral applications for the fixation devicesinclude utilization of the device for fastening soft tissue such ascapsule, tendon or ligament to bone. It may also be used to attach asynthetic material such as marlex mesh, to bone or allograft materialsuch as tensor fascia lata, to bone. In the process of doing so,retention of the material to bone may be accomplished with the collar asshown, or the pin and or collar may be modified to accept a suture orother material for facilitation of this attachment.

[0034] Specific examples include attachment of the posterior tibialtendon to the navicular bone in the Kidner operation. This applicationmay be accomplished using an appropriately sized implant of the presentinvention along with a washer with distally extending soft tissuespikes. Navicular-cuneiform arthrodesis may be performed utilizing thedevice and concurrent attachment of the tendon may be accomplished.Attachment of the tendon may be accomplished in the absence ofarthrodesis by altering the placement of the implant in the adjacentbone.

[0035] Ligament or capsule reattachment after rupture, avulsion ordetachment, such as in the ankle, shoulder or knee can also beaccomplished using the devices disclosed herein.

[0036] The fixation devices may be used in combination with semitubular, one-third tubular and dynamic compression plates, both ofmetallic and absorbable composition, if the collar is modified to matchthe opening on the plate.

[0037] The canulated design disclosed below can be fashioned to acceptan antibiotic impregnated rod for the slow adsorption of medicationlocally. This may be beneficial for prophylaxis, especially in openwounds, or when osteomyelitis is present and stabilization of fracturefragments is indicated.

[0038] A kit may be assembled for field use by military or sport medicalor paramedical personnel. This kit contains an implanting tool, and avariety of implant device size and types. The kit may include additionalcomponents such as sterilization or disinfectant materials, a skinstapler, bandages, gloves, and basic tools for emergent wound andfracture treatment. Antibiotic rods may be included for woundprophylaxis during transport.

[0039] Referring to FIG. 1, there is illustrated a posterior sideelevational view of the proximal portion of a femur 10, having afixation device 12 positioned therein. The proximal end of the femur 10comprises a head 14 connected by way of a neck 16 to the long body orshaft 17 of the femur 10. As illustrated in FIG. 1, the neck 16 issmaller in diameter than the head 14. The neck 16 and head 14 also lieon an axis which, on average in humans, crosses the longitudinal axis ofthe body 17 of the femur 10 at an angle of about 126°. The risk offracture at the neck 16 is thus elevated, among other things, by theangular departure of the neck 16 from the longitudinal axis of the body17 of femur 10 and also the reduced diameter of the neck 16 with respectto the head 14.

[0040] The greater trochanter 18 extends outwardly above the junction ofthe neck 16 and the body 17 of the femur 10. On the medial side of thegreater trochanter 18 is the trochanteric fossa 20. This depressionaccommodates the insertion of the obturator externus muscle. The lessertrochanter 21 is located posteromedially at the junction of the neck 16and the body 17 of the femur 10. Both the greater trochanter 18 and thelesser trochanter 21 serve for the attachment of muscles. On theposterior surface of the femur 10 at about the same axial level as thelesser trochanter 21 is the gluteal tuberosity 22, for the insertion ofthe gluteus maximus muscle. Additional details of the femur are wellunderstood in the art and not discussed in further detail herein.

[0041]FIG. 1 illustrates a fracture 24 which crosses the femurapproximately in the area of the greater trochanter 18. Fractures of theproximal portion of the femur 10 are generally classified as capital orsubcapital femoral neck fractures, intertrochanteric fractures andsubtrochanteric fractures. All of these fractures will be deemed femoralneck fractures for the purpose of describing the present invention.

[0042] Referring to FIGS. 1-4, the fixation device 12 comprises a body28 extending between a proximal end 30 and a distal end 32. The length,diameter and construction materials of the body 28 can be varied,depending upon the intended clinical application. In embodimentsoptimized for various fractures in an adult human population, the body28 will generally be within the range of from about 10 mm to about 150mm in length after sizing, and within the range of from about 2 mm toabout 8 mm in maximum diameter. The major diameter of the helicalanchor, discussed below, may be within the range of from about 2.7 mm toabout 12 mm. In general, the appropriate dimensions of the body 28 willvary, depending upon the specific fracture. In rough terms, for amalleolar fracture, shaft diameters in the range of from about 3 mm toabout 4.5 mm may be used, and lengths within the range of from about 25mm to about 70 mm. For condylar fractures, shaft diameters within therange of from about 3.5 mm to about 6.5 mm may be used with lengthswithin the range of from about 25 mm to about 70 mm. For collesfractures (distal radius and ulna), diameters within the range of fromabout 2.0 mm to about 4.5 mm may be used with any of a variety oflengths within the range of from about 6 mm to about 70 mm.

[0043] In one embodiment, the body 28 comprises titanium. However, aswill be described in more detail below, other metals or bioabsorbable ornonabsorbable polymeric materials may be utilized, depending upon thedimensions and desired structural integrity of the finished fixationdevice 12.

[0044] The distal end 32 of the body 28 is provided with a cancellousbone anchor or distal cortical bone anchor 34. Additional details of thedistal bone anchor are described below. In general, in a femoral neckapplication, distal bone anchor 34,is adapted to be rotationallyinserted into the cancellous bone within the head 14 of the femur 10, toretain the fixation device 12 within the femoral head.

[0045] Referring to FIGS. 3, 4, and 4A, the body 28 comprises a firstportion 36 and a second portion 38 that are coupled together at ajunction 40. In the illustrated embodiment, the first portion 36 carriesthe distal anchor 34 while the second portion 38 forms the proximal end30 of the body 28. The first and second portions 36, 38 are preferablydetachably coupled to each other at the junction 40. In the illustratedembodiment, the first and second portions 36, 38 are detachably coupledto each other via interlocking threads. Specifically, as best seen inFIG. 4A, the body 28 includes an inner surface 41, which defines acentral lumen 42 that preferably extends from the proximal end 30 to thedistal end 32 throughout the body 28. At the proximal end of the firstportion 36, the inner surface 41 includes a first threaded portion 44.The first threaded portion 44 is configured to mate with a secondthreaded portion 46, which is located on the outer surface 45 of thesecond portion 38. The interlocking annular threads of the first andsecond threaded portions 44, 46 allow the first and second portions 36,38 to be detachably coupled to each other. In one modified embodiment,the orientation of the first and second threaded portions 44, 46 can bereversed. That is, the first threaded portion 44 can be located on theouter surface of the first portion 36 and the second threaded portion 46can be located on the inner surface 41 at the distal end of the secondportion 38. Any of a variety of other releasable complementaryengagement structures may also be used, to allow removal of secondportion 38 following implantation, as is discussed below.

[0046] In a modified arrangement, the second portion 38 can comprise anyof a variety of tensioning elements for permitting proximal tension tobe placed on the distal anchor 34 while the proximal anchor is advanceddistally to compress the fracture. For example, any of a variety oftubes or wires can be removably attached to the first portion 36 andextend proximally to the proximal handpiece. In one such arrangement,the first portion 36 can include a releasable connector in the form of alatching element, such as an eye or hook. The second portion 38 caninclude a complementary releasable connector (e.g., a complementaryhook) for engaging the first portion 36. In this manner, the secondportion 38 can be detachably coupled to the first portion 36 suchproximal traction can be applied to the first portion 36 through thesecond portion as will be explained below. Alternatively, the secondportion 48 may be provided with an eye or hook, or transverse bar,around which or through which a suture or wire may be advanced, bothends of which are retained at the proximal end of the device. Followingproximal tension on the tensioning element during the compression step,one end of the suture or wire is released, and the other end may bepulled free of the device. Alternate releasable proximal tensioningstructures may be devised by those of skill in the art in view of thedisclosure herein.

[0047] The proximal end 30 of the fixation device is provided with aproximal anchor 50. Proximal anchor 50 is axially distally moveablealong the body 28, to permit compression of the fracture 24 as will beapparent from FIG. 1 and the description below. As will be explainedbelow, complimentary locking structures such as threads or ratchet likestructures between the proximal anchor 50 and the body 28 resistproximal movement of the anchor 50 with respect to the body 28 undernormal use conditions. The proximal anchor 50 preferably can be axiallyadvanced along the body 28 without rotation as will be apparent from thedisclosure herein.

[0048] In the illustrated embodiment, proximal anchor 50 comprises ahousing 52 such as a tubular body, for coaxial movement along the body28. As best seen in FIGS. 1 and 4, in a final position, the housing 52extends distally past the junction 40 between the first portion 36 andthe second portion 38. The housing 52 is provided with one or moresurface structures 54 such as a radially inwardly projecting flange 56(see FIGS. 4B and 4C), for cooperating with complementary surfacestructures 58 on the first portion 36 of the body 28. In the illustratedembodiment, the complimentary surface structures 58 comprise a series ofannular ridges or grooves 60. The surface structures 54 andcomplementary surface structures 58 permit distal axial travel of theproximal anchor 50 with respect to the body 28, but resist proximaltravel of the proximal anchor 50 with respect to the body 28.

[0049] For example, as best seen in FIG. 4B, the proximal end of theflange 56 is biased towards the longitudinal axis of the body 28. Assuch, when the proximal anchor 50 is urged proximally with respect tothe body 28, the flange 56 engages the grooves or ridges 60 of thecomplementary surface structures 58. This prevents proximal movement ofthe proximal anchor 50 with respect to the body 28. In contrast, as bestseen in FIG. 4C, when the proximal anchor 50 is moved distally withrespect to the body 28, the flange 56 can bend outwardly away from thebody 28 and the ridges 60 so as to allow the proximal anchor 50 to movedistally. Of course, those of skill in the art will recognize that thereare a variety of other complementary surface structures, which permitone way ratchet like movement. For example, a plurality of annular ringsor helical threads, ramped ratchet structures and the like forcooperating with an opposing ramped structure or pawl can also be used.In one embodiment, opposing screw threads are dimensioned to function asa ratchet.

[0050] Retention structures 58 are spaced axially apart along the body28, between a proximal limit 62 and a distal limit 64. The axialdistance between proximal limit 62 and distal limit 64 is related to thedesired axial working range of the proximal anchor 50, and thus therange of functional sizes of the fixation device 12. Thus, the presentinvention provides a bone fixation device which can provide compressionacross a fracture throughout a range of motion following the placementof the distal anchor. The distal anchor may be positioned within thecancellous and/or distal cortical bone, and the proximal anchor may bedistally advanced throughout a range to provide compression across thefracture without needing to relocate the distal anchor and withoutneeding to initially locate the distal anchor in a precise position withrespect to the proximal side of the bone. Providing a working rangethroughout which tensioning of the proximal anchor is independent fromsetting the distal anchor allows a single device to be useful for a widevariety of fractures, as well as eliminates the need for accurate devicemeasurement and accurate placement of the distal anchor. In manyapplications, the working range is at least about 10% of the overalllength of the device, and may be as much as 20% or 30% or more of theoverall device length. In the context of a femoral application, workingranges of up to about 10 mm or more may be provided, since estimateswithin that range can normally be readily accomplished within theclinical setting. In other applications, such as a metatarsal fracture,a working range in the area of from about 1 mm to about 2 mm may be allthat is necessary. The embodiments disclosed herein can be scaled tohave a greater or a lesser working range, as will be apparent to thoseof skill in the art in view of the disclosure herein.

[0051] The proximal anchor 50 includes a flange 66 that seats againstthe outer surface of the femur or tissue adjacent the femur. The flange66 is preferably an annular flange, to optimize the footprint or contactsurface area between the flange 66 and the femur. Circular or polygonalshaped flanges for use in femoral head fixation will generally have adiameter of at least about 4 mm greater than the adjacent body 28 andoften within the range of from about 4 mm to about 20 mm or more greaterthan the adjacent body 28.

[0052] In the illustrated embodiment, the bone contacting surface 68 ofthe flange 44 is tapered and generally faces the shaft 17 of the femur10. In other embodiments, the bone contacting surface 69 can resides inor approximately on a plane, which is perpendicular with respect to thelongitudinal axis of the body 28. In other embodiments, other angularrelationships between the bone contacting surface 68 of the flange 66and the longitudinal axis of the body 28 and housing 52 may be utilized,depending upon the anticipated entrance angle of the body 28 andassociated entrance point surface of the femur 10. In general, thelongitudinal axis extending through the head 14 and neck 16 of the humanfemur is inclined at an angle of approximately 126° from thelongitudinal axis of the long body 17 of the femur 10. Angles betweenthe longitudinal axis of body 28 and tissue contacting surface 68 withinthe range of from about 90° to about 140° will generally be utilized.

[0053] In a modified embodiment, the housing 52 of the proximal anchor50 can include one or more one or more barbs that extend radiallyoutwardly from the tubular housing 52. Such barbs provide for selftightening after the device has been implanted in the patient asdescribed in a co-pending U.S. Patent Application entitled DISTAL BONEFOR BONE FIXATION WITH SECONDARY COMPRESSION”, filed Nov. 13, 2001,which is hereby expressly incorporated by reference herein. The barbsmay be radially symmetrically distributed about the longitudinal axis ofthe housing 52. Each barb is provided with a transverse engagementsurface, for anchoring the proximal anchor 50 in the bone. Thetransverse engagement surface may lie on a plane which is transverse tothe longitudinal axis of the housing 50 or may be inclined with respectto the longitudinal axis of the tubular 50. In either arrangement, thetransverse engagement surface 43 generally faces the bone contactingsurface 68 of the flange 44. As such, the transverse engagement surfaceinhibits proximal movement of the proximal anchor with respect to thebone.

[0054] The clinician can be provided an array of proximal anchors 50 ofvarying angular relationships between the bone contacting surface 68 andthe longitudinal axis of the body 28 and housing 52 (e.g., 90°, 100°,110°, 120°, and 130°). A single body 28 can be associated with the arraysuch as in a single sterile package. The clinician upon identifying theentrance angle of the body 28 and the associated entrance point surfaceorientation of the femur 10 can choose the anchor 50 from the array withthe best fit angular relationship, for use with the body 28.

[0055] With particular reference to FIG. 3, the proximal end 30 of thebody 28 may be provided with a rotational coupling 70, for allowing thesecond portion 38 of the body 28 to be rotationally coupled to arotation device. The proximal end 30 of the body 28 may be desirablyrotated to accomplish one or two discrete functions. In one applicationof the invention, the proximal end 30 is rotated to remove the secondportion 38 of the body 28 following tensioning of the device across afracture or to anchor an attachment to the bone. Rotation of therotational coupling 70 may also be utilized to rotationally drive thedistal anchor into the bone. Any of a variety of rotation devices may beutilized, such as electric drills or hand tools, which allow theclinician to manually rotate the proximal end 30 of the body. Thus, therotational coupling 70 may have any of a variety of cross sectionalconfigurations, such as one or more flats or splines.

[0056] In one embodiment, the rotational coupling 70 comprises aproximal projection of the body 28 having an axial recess with apolygonal cross section, such as a hexagonal cross section. Therotational coupling 70 is illustrated as a female component, machined ormilled or attached to the proximal end 30 of the body 28. However, therotational coupling may also be in the form of a male element, such as ahexagonal or other noncircular cross sectioned projection.

[0057] As illustrated, the body 28 is cannulated to accommodateinstallation over a placement wire as is understood in the art. Thecross section of the illustrated central cannulation is circular but inother embodiments may be non circular, e.g., hexagonal, to accommodate acorresponding male tool for installation or removal of the secondportion 38 of the body 28 as will be explained below. In otherembodiments, the body 28 may partially or wholly solid.

[0058] In all of the embodiments illustrated herein, the distal anchor34 comprises a helical locking structure 72 for engaging cancellousand/or distal cortical bone. In the illustrated embodiment, the lockingstructure 72 comprises a flange that is wrapped around the axial lumen.The flange extends through at least one and generally from about two toabout 50 or more full revolutions depending upon the axial length of thedistal anchor and intended application. For most femoral neck fixationdevices, the flange will generally complete from about 2 to about 20revolutions. The helical flange 72 is preferably provided with a pitchand an axial spacing to optimize the retention force within cancellousbone, to optimize compression of the fracture.

[0059] The helical flange 72 of the illustrated embodiment has agenerally triangular cross-sectional shape (see FIG. 4). However, itshould be appreciated that the helical flange 72 can have any of avariety of cross sectional shapes, such as rectangular, oval or other asdeemed desirable for a particular application through routineexperimentation in view of the disclosure herein. The outer edge of thehelical flange 72 defines an outer boundary. The ratio of the diameterof the outer boundary to the diameter of the central lumen can beoptimized with respect to the desired retention force within thecancellous bone and giving due consideration to the structural integrityand strength of the distal anchor 34. Another aspect of the distalanchor 34 that can be optimized is the shape of the outer boundary andthe central core, which in the illustrated embodiment are generallycylindrical.

[0060] The distal end 32 and/or the outer edges of the helical flange 72may be atraumatic (e.g., blunt or soft). This inhibits the tendency ofthe fixation device 12 to migrate anatomically proximally towards thehip joint bearing surface after implantation (i.e., femoral headcut-out). Distal migration is also inhibited by the dimensions andpresence of the proximal anchor 50, which has a larger footprint thanconventional screws.

[0061] A variety of other arrangements for the distal anchor 32 can alsobe used. For example, the various distal anchors described in U.S.patent application Ser. No. 09/822,803, filed Mar. 30, 2001, andco-pending U.S. Patent Application entitled “DISTAL BONE FOR BONEFIXATION WITH SECONDARY COMPRESSION”, filed Nov. 13, 2001 can beincorporated into the fixation device 12 described herein. The entirecontents these applications are hereby expressly incorporated byreference. In particular, the distal anchor may comprise a singlehelical thread surrounding a central core, much as in a conventionalscrew, which has been cannulated to facilitate placement over a wire.Alternatively, a double helical thread may be utilized, with the distalend of the first thread rotationally offset from the distal end of thesecond thread. The use of a double helical thread can enable a greateraxial travel for a given degree of rotation and greater retention forcethan a corresponding single helical thread. Specific distal anchordesigns can be optimized for the intended use, taking into accountdesired performance characteristics, the integrity of the distal bone,and whether the distal anchor is intended to engage exclusivelycancellous bone or will also engage cortical bone.

[0062] With particular reference to FIGS. 2 and 5, the fixation devicemay include an antirotation lock between the first portion 36 of thebody 28 and the proximal collar 50. In the illustrated embodiment, thefirst portion 36 includes a pair of flat sides 80, which interact withcorresponding flat structures 82 in the proximal collar 50. One or threeor more axially extending flats may also be used. As such, rotation ofthe proximal collar 50 is transmitted to the first portion 36 and distalanchor 34 of the body 28. Of course, those of skill in the art willrecognize various other types of splines or other interfit structurescan be used to prevent relative rotation of the proximal anchor and thefirst portion 36 of the body 28.

[0063] To rotate the proximal collar, the flange 66 is preferablyprovided with a gripping structure to permit an insertion tool to rotatethe flange 66. Any of a variety of gripping structures may be provided,such as one or more slots, flats, bores or the like. In one embodiment,the flange 44 is provided with a polygonal, and, in particular, apentagonal or hexagonal recess 84. See FIG. 4.

[0064] In use, the clinician first identifies a patient having afracture to be treated, such as a femoral neck fracture, which isfixable by an internal fixation device. The clinician accesses theproximal femur, reduces the fracture if necessary and selects a bonedrill and drills a hole 90 (see FIG. 6A) in accordance with conventionaltechniques. Frequently, the hole 90 has a diameter within the range fromabout 3 mm to about 8 mm. This diameter may be slightly larger than thediameter of the distal anchor 34. The hole 90 preferably extends up toor slightly beyond the fracture 24.

[0065] A fixation device 12 having an axial length and outside diametersuitable for the hole 90 is selected. The distal end 32 of the fixationdevice 12 is advanced distally into the hole 90 until the distal anchor34 reaches the distal end of the hole 90. The proximal anchor 50 may becarried by the fixation device 12 prior to advancing the body 28 intothe hole 90, or may be attached following placement of the body 28within the hole 90. Once the body 28 and proximal anchor 50 are inplace, the clinician may use any of a variety of driving devices, suchas electric drills or hand tools to rotate the proximal anchor 50 andthus cancellous bone anchor 34 into the head of the femur.

[0066] Once the anchor 34 is in the desired location, proximal tractionis applied to the proximal end 30 of body 28, such as by conventionalhemostats, pliers or a calibrated loading device, while distal force isapplied to the proximal anchor 50. In this manner, the proximal anchor50 is advanced distally until the anchor 50 fits snugly against theouter surface of the femur or tissue adjacent the femur and the fracture24 is completely reduced as shown in FIG. 6B. Appropriate tensioning ofthe fixation device 12 is accomplished by tactile feedback or throughthe use of a calibration device for applying a predetermined load on theimplantation device. One advantage of the structure of the presentinvention is the ability to adjust compression independently of thesetting of the distal anchor 34.

[0067] Following appropriate tensioning of the proximal anchor 50, thesecond portion 38 of the body 28 is preferably detached from the firstportion 36 and removed. See FIG. 6C. In the illustrated embodiment, thisinvolves rotating the second portion 38 with respect to the firstportion via the coupling 70. In connection with many of the fracturesidentified previously herein, a single fixation device 12 may be allthat is clinically indicated. However, two or three or more fixationdevices 12 may be utilized to reduce a single fracture, depending uponthe location and physical requirements of the fractured portion of thebone. For example, in the case of proximal femoral fractures of the typeillustrated herein, typically at least two and preferably three fixationdevices 12 will be implanted to span the femoral neck. The use of threefixation devices 12 desirably provides sufficient compression across thefracture, as well as minimizes the risk of rotation of the head of thefemur around the axis of a single fixation device 12. The proximal endof the fixation devices may be connected together such as through athree-holed plate or rod, or may be independent of each other.

[0068] Following removal of the second portion 38 of each body 28, theaccess site may be closed and dressed in accordance with conventionalwound closure techniques.

[0069] In a modified arrangement, the second portion 38 may form part ofthe driving device, which is used to rotate the proximal anchor 50 andthus cancellous bone anchor 34 into the head of the femur. The secondportion 38 is used to apply proximal traction so as to compress thefracture. After appropriate tensioning, the second portion 38 can bede-coupled from the first portion 36 and removed with the drivingdevice.

[0070] In the foregoing variation, the second portion 38 may beconnected to a rotatable control such as a thumb wheel on the deploymentdevice. A container may be opened at the clinical site exposing theproximal end of the implant, such that the distal end of the secondportion 38 may be removably coupled thereto. Proximal retraction of thehand tool will pull the implant out of its packaging. The implant maythen be positioned within the aperture in the bone, rotated to set thedistal anchor, and the hand piece may be manipulated to place proximaltraction on the second portion 38 while simultaneously distallyadvancing the proximal anchor. Following appropriate tensioning acrossthe fracture, the second portion 38 may be disengaged from the implant,and removed from the patient. In the example of a threaded engagement,the second portion 38 may be disengaged from the implant by rotating athumb wheel or other rotational control on the hand piece. In analternate embodiment, such as where the second portion 38 comprises apull wire, following appropriate tensioning across the fracture, a firstend of the pull wire is released such that the pull wire may be removedfrom the implant by proximal retraction of the second end which may beattached to the hand piece.

[0071] Preferably, the clinician will have access to an array offixation devices 12, having, for example, different diameters, axiallengths and, if applicable, angular relationships. These may be packagedone per package in sterile envelopes or peelable pouches, or indispensing cartridges which may each hold a plurality of devices 12.Upon encountering a fracture for which the use of a fixation device isdeemed appropriate, the clinician will assess the dimensions and loadrequirements, and select a fixation device from the array, which meetsthe desired specifications.

[0072] In some instances, a clinician may want to introduce two or morefixation devices 12 into the femoral head 14 to secure the fracture 24.This may be desirable if the clinician determines that, based upon thenature of the fracture 24, there is a possibility that the head 14 ofthe femur 10 could rotate about a single fixation device 12. Even minorrotation can inhibit the healing of the fracture. Significant rotationcan result in failure of the fixation device or necrosis of the femoralhead. Two or more fixation devices 12 may also be desirable where thedirection of the fracture is generally parallel to the axis ofimplantation as is understood in the art.

[0073] The fixation device 12 of the present invention may also be usedin combination with intramedullary nails or rods, as will be understoodby those of skill in the art.

[0074] The fixation device 12 of the present invention may be used inany of a wide variety of anatomical settings beside the proximal femur,as has been discussed. For example, lateral and medial malleolarfractures can be readily fixed using the device of the presentinvention. Referring to FIG. 7, there is illustrated an anterior view ofthe distal fibula 120 and tibia 122. The fibula 120 terminates distallyin the lateral malleolus 124, and the tibia 122 terminates distally inthe medial malleolus 126.

[0075] A fixation device 12 in accordance with the present invention isillustrated in FIG. 7 as extending through the lateral malleolus 124across the lateral malleolar fracture 128 and into the fibula 120.Fixation device 12 includes a distal anchor 34 for fixation within thefibula 120, an elongate body 28 and a proximal anchor 50 as has beendiscussed.

[0076]FIG. 7 also illustrates a fixation device 12 extending through themedial malleolus 126, across a medial malleolar fracture 130, and intothe tibia 122. Although FIG. 7 illustrates fixation of both a lateralmalleolar fracture 128 and medial malleolar fracture 130, eitherfracture can occur without the other as is well understood in the art.Installation of the fixation devices across malleolar fractures isaccomplished utilizing the same basic steps discussed above inconnection with the fixation of femoral neck fractures.

[0077] The fixation devices of the present invention may be made fromeither conventional bioabsorbable materials or conventionalnon-absorbable materials, combinations thereof and equivalents thereof.In addition, natural materials such as allografts may be used. Examplesof absorbable materials include homopolymers and copolymers of lactide,glycolide, trimethylene carbonate, caprolactone, and p-dioxanone andblends thereof. The following two blends may be useful: 1) the blend ofpoly(p-dioxanone) and a lactide/glycolide copolymer, as disclosed inU.S. Pat. No. 4,646,741 which is incorporated by reference and (2) theglycolide-rich blend of two or more polymers, one polymer being a highlactide content polymer, and the other being a high glycolide contentdisclosed in U.S. Pat. No. 4,889,119 which is incorporated by reference.Additional bioabsorbable materials are disclosed in copendingapplication Ser. No. 09/558,057 filed Apr. 26, 2000, the disclosure ofwhich is incorporated in its entirety herein by reference.

[0078] The fixation devices may also be made from conventionalnon-absorbable, biocompatible materials including stainless steel,titanium, alloys thereof, polymers, composites and the like andequivalents thereof. In one embodiment, the distal anchor comprises ametal helix, while the body and the proximal anchor comprise abioabsorbable material. Alternatively, the distal anchor comprises abioabsorbable material, and the body and proximal anchor comprise eithera bioabsorbable material or a non-absorbable material. As a furtheralternative, each of the distal anchor and the body comprise anon-absorbable material, connected by an absorbable link. This may beaccomplished by providing a concentric fit between the distal anchor andthe body, with a transverse absorbable pin extending therethrough. Thisembodiment will enable removal of the body following dissipation of thepin, while leaving the distal anchor within the bone.

[0079] The components of the invention (or a bioabsorbable polymericcoating layer on part or all of the anchor surface), may contain one ormore bioactive substances, such as antibiotics, chemotherapeuticsubstances, angiogenic growth factors, substances for accelerating thehealing of the wound, growth hormones, antithrombogenic agents, bonegrowth accelerators or agents, and the like. Such bioactive implants maybe desirable because they contribute to the healing of the injury inaddition to providing mechanical support.

[0080] In addition, the components may be provided with any of a varietyof structural modifications to accomplish various objectives, such asosteoincorporation, or more rapid or uniform absorption into the body.For example, osteoincorporation may be enhanced by providing amicropitted or otherwise textured surface on the components.Alternatively, capillary pathways may be provided throughout the bodyand collar, such as by manufacturing the anchor and body from an open cell foam material, which produces tortuous pathways through the device.This construction increases the surface area of the device which isexposed to body fluids, thereby generally increasing the absorptionrate. Capillary pathways may alternatively be provided by laser drillingor other technique, which will be understood by those of skill in theart in view of the disclosure herein. In general, the extent to whichthe anchor can be permeated by capillary pathways or open cell foampassageways may be determined by balancing the desired structuralintegrity of the device with the desired reabsorption time, taking intoaccount the particular strength and absorption characteristics of thedesired polymer.

[0081] One open cell bioabsorbable material is described in U.S. Pat.No. 6,005,161 as a poly(hydroxy) acid in the form of an interconnecting,open-cell meshwork which duplicates the architecture of human cancellousbone from the iliac crest and possesses physical property (strength)values in excess of those demonstrated by human (mammalian) iliac crestcancellous bone. The gross structure is said to maintain physicalproperty values at least equal to those of human, iliac crest,cancellous bone for a minimum of 90 days following implantation. Thedisclosure of U.S. Pat. No. 6,005,161 is incorporated by reference inits entirety herein.

[0082] The components of the present invention may be sterilized by anyof the well known sterilization techniques, depending on the type ofmaterial. Suitable sterilization techniques include heat sterilization,radiation sterilization, such as cobalt 60 irradiation or electronbeams, ethylene oxide sterilization, and the like.

[0083] The specific dimensions of any of the bone fixation devices ofthe present invention can be readily varied depending upon the intendedapplication, as will be apparent to those of skill in the art in view ofthe disclosure herein. Moreover, although the present invention has beendescribed in terms of certain preferred embodiments, other embodimentsof the invention including variations in dimensions, configuration andmaterials will be apparent to those of skill in the art in view of thedisclosure herein. In addition, all features discussed in connectionwith any one embodiment herein can be readily adapted for use in otherembodiments herein. The use of different terms or reference numerals forsimilar features in different embodiments does not imply differencesother than those which may be expressly set forth. Accordingly, thepresent invention is intended to be described solely by reference to theappended claims, and not limited to the preferred embodiments disclosedherein.

1-9. (Canceled)
 10. A method of treating a femoral fracture, comprisingthe steps of: drilling a bore distally into the femur in the directionof a fracture; advancing into the bore a fixation device that comprisesa body having a first portion that forms a cancellous bone anchor and asecond portion that is removably attached to the first portion and formsa proximal end of the body; rotating a proximal anchor carried by thebody of the fixation device to rotate the cancellous bone anchor andengage the cancellous bone anchor with bone tissue distal of the femoralfracture; and advancing the proximal anchor distally along the fixationdevice to compress the fracture; and separating and removing the secondportion of the body from the first portion of the body.
 11. A method oftreating a femoral fracture as in claim 10, wherein the drilling stepcomprises drilling the bore along an axis which extends through thefemoral neck and into the head of the femur.
 12. A method of treating afemoral fracture as in claim 10, wherein the cancellous bone anchorcomprises a helical anchor
 13. A method of treating a femoral fractureas in claim 10, wherein the advancing a proximal anchor step comprisesaxially advancing the proximal anchor without rotating the proximalanchor with respect to the fixation device.
 14. A method of treating afemoral fracture as in claim 10, wherein the fracture is a femoral neckfracture, an intertrochanteric fracture or a subtrochanteric fracture.15. (Canceled)
 16. A method of treating a femoral fracture as in claim10, wherein separating and removing the second portion from the firstportion comprises rotating the second portion with respect to the firstportion.
 17. A method of securing a first bone fragment to a second bonefragment, comprising the steps of: drilling a bore through the firstbone fragment in the direction of the second bone fragment; providing afixation device that comprises a body having a first portion that formshelical distal anchor and a second portion that forms a proximal end ofthe body; removably coupling the first portion of the body to the secondportion of the body; advancing through the bore the fixation device;rotating a proximal anchor carried by the body of the fixation device torotate and secure the distal anchor of the fixation device to the secondfragment; and axially advancing the proximal anchor of the fixationdevice to engage the first fragment.
 18. A method of securing a firstbone fragment to a second bone fragment as in claim 17, wherein thesecond bone fragment comprises the head of a femur.
 19. A method ofsecuring a first bone fragment to a second bone fragment as in claim 17,wherein the second bone fragment comprises the tibia.
 20. A method ofsecuring a first bone fragment to a second bone fragment as in claim 17,wherein the second bone fragment comprises the fibula.
 21. A method ofsecuring a first bone fragment to a second bone fragment as in claim 17,wherein the second bone fragment comprises the femur.
 22. A method ofsecuring a first bone fragment to a second bone fragment as in claim 17,wherein the first bone fragment comprises the femur.
 23. A method ofsecuring a first bone fragment to a second bone fragment as in claim 17,wherein the first bone fragment comprises a condyle.
 24. A method ofsecuring a first bone fragment to a second bone fragment as in claim 17,wherein the drilling step comprises drilling a bore through the firstbone fragment and into the second bone fragment.
 25. A method ofsecuring a first bone fragment to a second bone fragment as in claim 17,further comprising separating and removing the second portion of thebody from the first portion of the body.
 26. A method of securing afirst bone fragment to a second bone fragment as in claim 25, whereinseparating and removing the second portion of the body from the firstportion of the body comprises rotating the second portion with respectto the first portion. 27-33. (Canceled)
 34. A method of fixing a firstportion of a bone to a second portion of a bone, comprising the stepsof: providing a fixation device, having a proximal anchor, a distalanchor and a removable extension; advancing the device across afracture; rotating the distal anchor to secure the distal anchor in thesecond portion of the bone; distally advancing the proximal anchoragainst the first portion of the bone while applying proximal tractionon the removable extension; and removing the removable extension.
 35. Amethod of fixing a first portion of a bone to a second portion of a boneas in claim 34, wherein removing the removable extension comprisesrotating the removable extension with respect to the fixation device.36. A method of fixing a first portion of a bone to a second portion ofa bone, as in claim 34, wherein the second portion of a bone comprisesthe head of a femur.